Inflated roof



Aug. 29, 1967 A; TR DER ET AL 3,338,000

IIIIIIIIII OF United States Patent INFLATED ROOF Albert A. Ostrander, deceased, late of Pleasantville, N.Y., by Marian Depew Ostrander, administrator, 48 Cedar Ave., Pleasantville, N.Y. 10570; Robert E. Hart, RED. 1, Peekskill, N.Y. 10566; and Angelo. L. Gutierrez, 11 Riverside Drive 10023; and Elaine C. Reder, 31 W. 11th St. 10011, both of New York, N.Y.

Filed Apr. 12, 1965, Ser. No. 456,017 9 Claims. (Cl. 52-2) This is a continuation-in-part of application Ser. No. 243,000 filed December 7, 1962, and now abandoned.

This invention relates in general to inflated roofs and more particularly to buildings with a cable supported inflated roof in which the interior of the building may be maintained at normal atmospheric pressure.

This invention is directed to devising a light weight, mobile building. It is the roof, in particular, which forms the heart of this invention and which makes possible the light weight and mobile building described herein.

A major problem in any structural design is in the appropriate resolution of forces in the structure so as to minimize high stress areas. The more effectively these stresses are minimized, the less requirement there is for heavy structures.

Accordingly, it is an important object of this invention to provide a roof structure which will translate all vertical forces and weights on and in the roof to the supporting walls as vertical forces and thus avoid much of the horizontal stress which walls in prior art buildings had to withstand.

The inflated envelope as a roof has many advantages in a mobile structure. Thermal insulation, low weight, transportability, and low erection cost are all factors that prompt the use of an inflated envelope in a light weight and mobile building. However, the inflated envelope will sag'with time.

Thus it is another object of this invention to provide an inflated roof in which there is control over the curvature of the inner ceiling.

It is still another object of this invention to provide a roof design which can be made and erected inexpensively.

' A broad object of this invention is to provide a mobile structure which has versatility of use and a distinctive, pleasing appearance.

A further object of this invention is to provide a structure with the above characteristics in which the structural members may be confined to the perimeter of the building.

A still further object of this invention is to provide a structure with an inflatable roof and an interior which is at normal atmospheric pressure.

Other objects and a fuller understanding of this invention may be obtained by referring to the following description and claims, taken in conjunction with the accompanying drawings, in Which:

FIG. 1 is a side view in cross section of one embodiment of this invention showing an inflated two membrane roof envelope and the peripheral self-braced members which form the side walls of the structure;

FIG. 2 is a plan view of a structural subassembly comprising the peripheral self-braced members, the compression member, the central connector and the lines which support the envelope;

FIG. 3 is a plan view of another embodiment of the invention.

With reference to the drawings, FIG. 1 illustrates an embodiment of this invention in which the peripheral self-braced members (side walls) 12 have been left exposed to allow the free circulation of air and in which the area enclosed is entirely unobstructed. If so desired,

and the use allows, the side walls 12 might be enclosed.

FIG. 1 shows the double convex envelope 16, one membrane 18 of which provides the exterior roof of the building and the other membrane 20 of which provides a ceiling for the interior. The compression member 22 encircles the buildings periphery and, as discussed below, reacts with a connector 24 and flexible lines 26 in a manner such that substantially no horizontal or bending stresses are transmitted to the side walls 12 due to vertical loads.

More specifically, as shown in FIG. 2, flexible cables 26 are suspended between a ring 24 (which is thereby placed under tension) and the vertices of a level, multilateral member 22 (which is thereby placed under compression). The compression member 22 is mounted atop the structures side wall 12, the side wall 12 thereby supporting the entire roof assembly. A double-convexenvelope 16 is aflixed atop this framework. This may be done by lacing the edges of the envelope 16 to the compression member 22. The lower membrane 20 of the envelope 16 is designed such that when the envelope 16 is inflated, the vertical profile of this membrane 20 approximates that of the flexible lines 26.

When the envelope 16 is inflated, its Weight is thus supported by the flexible lines 26 which in turn are carried by the compression member 22. The flexible lines 26, when loaded by the inflated envelope 16, subject the ring 24 to tensile stresses and the compression member 22 to compressive stresses.

If the compression member 22 is fabricated so as to be a substantially rigid member, the horizontal components of the above-discussed forces are resolved by the compression member 22 and are not transmitted to the side wall 12. Thus, only the vertical components of the forces arising from the weight of the envelope 16 and other vertical loads are transmitted to the side walls 12 which may therefore be constructed of lighter-duty material than would otherwise be needed in a building of equivalent size. In addition, the structures foundation requirements are minimized. Of course, the side walls 12 will still receive bending and horizontal stresses from other sources, for example, wind.

A consideration of the relation between the cables 26 and the rest of the structure will highlight some of the more significant achievements of this invention. The cables 26 are crucial in controlling the curvature of the inner ceiling 20. This control of ceiling 20 sag makes it possible to use the roof with outer walls of reasonable height. Thus, the cables 26 make it possible to use the roof in a wide variety of applications.

Although curvature control of the inner ceiling 20 is the more significant purpose of the cables 26, it should also be noted that the cables serve an evident safety function. In addition, the cables 26 may be used as a frame from which to hang various elements such as electrical equipment and decorative items. 1

The cables 26 may be linked to the compression member 22 through turnbuckles. In this fashion the sag in the cables 26 may be adjusted to the design sag which has been tailored into the ceiling membrane 20. In otherdesigns, where the turnbuckles are not desired, the length of the cables 26 has to be calculated so that they will approximately conform to the sag tailored into the ceiling membrane 20. Where ceiling sag is controlled to a relatively small amount it is possible to entirely avoid tailoring the ceiling membrane. In such situations, the ceiling membrane 20 may be cut flat and the membrane 20 will stretch to provide the called for sag. v

In connection with the above discussion of the cable 26 control over ceiling membrane-20 sag, it must be remembered that the tailoring of the ceiling membrane 20 is not adequate by itself to control sag simply because the ceiling membrane 20 will stretch with time and will not retain its originally tailored shape.

In almost allcases, the upper membrane 18 will be tailored to achieve the desired vertical contour. The upper membrane 18 will usually be designed with a fairly prominent profile in order to stabilize the envelope 16 against Wind and to assure that rain will run off the roof. The lower membrane 20 will usually be designed with a less prominent profile in order to enlarge the buildings interior.

The internal pressure of the envelope 16 need not be higher than is necessary to inflate the envelope 16 and to maintain a substantially constant desired configuration. The interior of the envelope 16 may be a single pressure chamber or may consist of several independent chambers, either vertically or horizontally divided. A multiplicity of chambers may be desired to increase the insulating properties of the roof. However, it is a feature of this invention that multiple chambers need not be employed. The shape of the envelope 16 is determined by the tailoring of the roof membrane 18, the tailoring of the ceiling membrane 20, and the sag control imposed by the cables 26. The dividing walls between chambers should be designed so as not to impose a further limitation on the envelope 16 configuration.

The addition of chambers within the envelope 16 is within the scope of this invention as long as the contour of the roof membrane 18 and the ceiling membrane 20 are determined by the tailoring of these membranes and by the sag of the cables 26.

The number of chords in the compression member 22 is not fixed but rather varies as a function of such factors as the size of the building and whether the design requirements include a desire for structural members which are easy to handle and to transport. Thus, other embodiments of the same invention might have many fewer chords than those illustrated in FIG. 2. It would be possible, in the appropriate circumstance, for an embodiment of this invention to have a triangular compression member of three chords or a quadrilateral of four chords; in fact, rather than consisting of chord-like members, the compression member 22 might instead be a rigid circular ring.

In order to minimize the size and weight and strength of the structural members, it is desirable for the compression member 22 to have a reasonably large number of chords which are connected to form a generally circular compression member 22, much like the one illustrated in FIG. 2. In general, variations from a circular rim envelope 16 and generally circular compression member 22 will require either a stronger compression member 22 (and thus a heavier and more expensive compression member 22) or a degree of transverse support for the roof structure from the side walls 12 (and thus a heavier and more expensive side wall 12 construction). For example, if the envelope 16 had an elliptical perimeter (and thus the compression member were elliptical), the forces transmitted to the compression member by the cables would create major forces other than compressive forces within the compression member. There would be forces tending to make the elliptical compression member circular. These forces would have to be designed for by either making the compression member and/or the side walls stronger than necessary in a circular construction.

Although the invention has been described with a certain degree of particularity, it is understood that the disclosure has been made only by way of example and that a number of changes may be made in the details of constr-uction without departing from the spirit and scope of the invention as claimed.

For example, by regulating the temperature of the gas within the envelope 16, it is possible to regulate the temperature of the air within the building itself.

By using a translucent material for the two membranes 18 and 20 of the envelope 16, it is possible to employ a single light source and simultaneously illuminate both the exterior of the envelope 16 and the interior of the building. It is also possible, by the use of translucent material, to admit considerable daylight into the building.

In the specification and claims, the term cable has been used as a generic term for any flexible line. It is to be understood herein that a wide range of flexible lines is denoted by the word cable.

Similarly, the compression member is to be understood in a broad sense as referring to a structure which circumscribes the rim of the envelope 16 and to which the cables 26 are attached so that balanced horizontal forces can be resolved within the compression member without being transmitted to the side walls.

As a further example, the tension ring 24 serves a very useful function as a terminus for the cables 26 but is not essential to the broadest concept of this invention. The tension ring 24 could Well be eliminated and each cable 26 made to span the entire diameter of the envelope 16. In such a case the cables 26 would have to pass under one another but could be oflset in such a fashion as not to bunch up at one point.

Referring to FIG. 3, a circularcompression ring 22' or other smooth curve compression ring can be used instead of a compression ring 22 as described above. Also, in addition to securing a plurality of cables 26 between a compression member 22 and a tension ring 24' a plurality of cables 27 may be secured at each end to spaced points on the compression member 22. The cables 27 which are attached to a common position on the compression member have a geometric line of symmetry such that the included angles between the lines of symmetry and compression member are equal.

We claim:

1. A roof structure comprising:

an inflated envelope having an upper membrane and a' lower membrane, the vertical profile of said upper membrane being maintained by a difference in pressure between the inside of said envelope and the atmosphere,

a compression member circumscribing the rim of said envelope and spaced from the ground, said compression member lying substantially in one plane, and

a plurality of flexible cables attached to said compression member to support said envelope, said lower membrane of said envelope resting on and being supported by said flexible cables, those ones of said cables attached to a common position on said compression member having a geometric line of symmetry and such that the included angles between said line of symmetry and said compression member are equal, each of said cables forming a smooth curve having a convex form when viewed from below.

2. The roof structure of claim 1 in which only one of said cables is attached to a given position on said compression member so that said geometric line of symmetry is coincident with the curve of said cable.

3. A roof structure comprising:

an inflated envelope having an upper membrane and a lower membrane, the vertical profile of said upper membrane being maintained by a difference in pressure between the inside of said envelope and the atmosphere,

a compression member circumscribing the rim of said envelope and spaced from the ground, said compression member being in the form of a continuous closed curve lying substantially in one plane, and

a plurality of flexible cables attached to said compression member to support said envelope, said lower membrane of said envelope resting on and being supported by said flexible cables, said cables being at-. tached to said compression member such that those of said cables that are attached to a common position on said compression member have a geometric line of symmetry perpendicular to the line of tangency 8. A roof structure comprising: to said compression member at said common position, an inflated envelope having an upper membrane and each of said cables forming a smooth curve having a a lower membrane, the vertical profile of said upper convex form when viewed from below. membrane being maintained by a dilference in pres- 4. The roof structure of claim 3 in which only one of 5 sure between the inside of said envelope and the atsaid cables is attached to said compression member at mosphere, a given position so that geometric line of symmetry is a regular polygonal compression member circumscribcoincident with the curve of the cable. ing the rim of said envelope and spaced from the 5. A roof structure comprising:

ground, said compression member being comprised an inflated envelope having an upper membrane and 10 of a plurality of equal length struts forming end-toa lower membrane, the vertical profile of said upper end joints with one another and all lying substantially membrane being maintained by a diflerence in presin a single plane, and sure between the inside of said envelope and the ata plurality of flexible cables attached to said compresmosphere, sion member to support said envelope, said lower a circular compression ring circumscribing the rim of membrane of said envelope resting on and being supsaid envelope and spaced from the ground, and ported by said flexible cables, each one of said cables a plurality of flexible cables attached to said compresbeing attached to a separate one of said joints between sion ring to support said envelope, said lower mem adjacent struts on said compression member, the brane of said envelope resting on and being supported orthogonal projection of each one of said cables on by said flexible cables, each of said cables being atsaid plane of said compression member being a line tached to a separate position on said compression that bisects the angle between the adjacent struts at ring, said separate positions being equally spaced the respective ones of said joints, each of said cables around said compression ring, each of said cables forming a smooth curve having a convex form when being perpendicular to the line of tangency to said viewed from below. compression ring at each point of attachment, each 9. In a building having side walls, a roof structure of said cables forming a smooth curve having a convex comprising: form when viewed from below. an inflated envelope having an upper membrane and a 6. A roof structure comprising: lower membrane, the vertical profile of said upper an inflated envelope having an upper membrane and membrane being maintained by a difference in presa lower membrane, the vertical profile of said upper sure between the inside of said envelope and the membrane "being maintained by a difference in presatmosphere, sure between the inside of said envelope and the a compression member circumscribing the perimeter of atmosphere, said envelope and attached to the rim .of said envea compression member circumscribing the rim of said lope, a plurality of flexible cables, each cable being envelope and spaced from the ground, said compresattached at a first end to said compression member, sion member being comprised of a plurality of struts and forming end-to-end joints with one another and all a tension member centrally held under said lower memlying substantially in a single plane, and brane by the second ends of said cables, a plurality of flexible cables attached to said com pressaid lower end of said envelope resting on and supported sion member to support said envelope, said lower by said flexible cables, membrane of said envelope resting on and being su-pwhereby compression forces in said compression memported by said flexible cables, said cables being ather minimize the impact on said side walls of horitached to said compression member at said joints zontal forces due to the weight of said roof and any between adjacent struts, those of said cables that are items hung from said roof. attached to any one of said joints having a geometric 5 line of symmetry such that orthogonal projection of References Cited sald me of s m on f Plane of Sald Architectural Record, pages 211-216, September 1956. compression member is a hne that bisects the angle Civil Engine ri P g 64-65, y 195 between the adjacent struts forming said one of said Engineering Newspecord, pages 3840 Aug. 20 1959 oints, each of said cables forming a smooth curve having a convex form when viewed from below.

REINALDO P. MACHADO, Primary Examiner. HARRISON R. MOSELEY, Examiner. L. J. SANTISI, A. I. BREIER, Assistant Examiners.

7. The roof structure of claim 6 wherein only one of said cables are attached to any one of said joints so that said geometric line of symmetry is coincident with the curve of the cable. 

1. A ROOF STRUCTURE COMPRISING: AN INFLATED ENVELOPE HAVING AN UPPER MEMBRANE AND A LOWER MEMBRANE, THE VERTICAL PROFILE OF SAID UPPER MEMBRANE BEING MAINTAINED BY A DIFFERENCE IN PRESURE BETWEEN THE INSIDE OF SAID ENVELOPE AND THE ATMOSPHERE, A COMPRESSION MEMBER CIRCUMSCRIBING THE RIM OF SAID ENVELOPE AND SPACED FROM THE GROUND, SAID COMPRESSION MEMBER LYING SUBSTANTIALLY IN ONE PLANE, AND PLURALITY OF FLEXIBLE CABLES ATTACHED TO SAID COMPRESSION MEMBER TO SUPPORT SAID ENVELOPE, SAID LOWER 